The present invention relates to a driving device employed in a window regulator (hereinafter referred to as "driving device"), and, more particularly, to the driving device which can surely prevent a crank lever from shaking due to vibration of a car, or the like, or which can always maintain tension of wires in a suitable range.
Until now, a window regulator shown in FIG. 14 has been known. Namely, the window regulator comprises two wires 51, 52 being laid in the window regulator in tense condition; a driving device 54 having a drum 53, for winding the wires 51, 52 in the opposite directions, to which one end of each wire is connected; and a driven device 57 having a carrier plate 56, capable of sliding on a guide rail 55, to which the other end of each wire 51, 52 is connected. When the drum 53 is rotated in the direction of Arrow A or B, one of the wires 51, 52 is wound around the drum 53 and the other wire is unwound from the drum 53, and as a result, the carrier plate 56 moves in the direction of Arrow C or D.
However, elastic elongation and permanent elongation generally generate in the wires, such as stranded metallic wires, in the course of the operation. If permanent elongation and/or looseness generate in the wires, tension of the wires is lost and it is impossible for the driving device 54 to correctly transmit the operational force to the driven device 57. With respect to the above described window regulator, mechanisms for automatically eliminating permanent elongation generated in the wires are discussed in U.S. Pat. Nos. 4,400,993 and 4,440,354.
The mechanisms basically comprise two divided drums, i.e. a first drum and a second drum having ratchet teeth 63, 64 at each facing side, as indicated by two-dot chain line in FIG. 14. The mechanisms can eliminate permanent elongation by means of relative rotation of the first drum 53a and the second drum 53b.
However, in case that such mechanisms are employed in the driving device, excess elastic elongation is generated occasionally. For example, when sliding resistance between the carrier plate 56 and the guide rail 55 increases temporarily, or when the crank lever is rotated in the direction of Arrow B after the first wire 51 has entirely wound up, (i.e. after the carrier plate 56 reaches the stopper 58), the relative rotation of the first drum 53a and the second drum 53b is excessively performed. As a result, excessive elastic elongation generates in the first wire 51 (and the second wire 52). Further, as a result, the mesh of the ratchet teeth 63, 64 might advance in a state of eliminating suitable play. It is disadvantageous that such excessive elastic elongation of the wires causes permanent elongation, and causes the pulley 59 and rotational shafts of other connecting members to be bended, and causes the operation of the crank lever 61 to be heavy.
Also, in case that the crank lever is rotated in the direction of Arrow A, one fact that the above sliding resistance increases, or another fact that the crank lever is rotated in the direction of Arrow A after the carrier plate 56 has reached the opposite stopper 60 causes the ratchet teeth 63, 64 to fly over with each other, in spite of meshing direction of both ratchet teeth (this phenomenon is hereinafter referred to as "flying phenomenon"). The flying phenomenon causes wires to be loosed. By means of wearing out addendums of the ratchet teeth 63, 64, it tends to occur the flying phenomenon.
By the way, a mechanism for eliminating permanent elongation or looseness of wires, having a brake spring located between the driving shaft 65 and the drum 53, has been known.
The brake spring 92 shown in FIG. 15 is employed to prevent a window glass from being raised or lowered, except that the crank lever 61 or the shaft 96 is positively rotated. In such driving device, operations of the brake spring 92 are, as described later, realized by means of association of a notch portion 95 of a associating member 94 and a associating projection 97 of the drum 54 with some play, for example, an angle of 30 degrees, in the rotational direction. In that case, the drum 54 is not fixed to the shaft 96, and the associating member 94 is fixed to the shaft 96.
As shown in FIG. 15, when the crank lever 61 is rotated in the direction of Arrow B, one side surface 95a of the notch portion 95 pushes a nail 92a of the brake spring 92 in the direction of Arrow B. Accordingly, the locking operation of the brake spring (due to the frictional resistance of the brake spring and an inner peripheral surface of the housing) is released, since the diameter of the brake spring 92 is reduced. Accordingly, since the rotation of the associating memeber 94 causes the notch portion 95 and the associating projection 97 to associate with each other, the drum 54 can be rotated in the direction of Arrow B.
A rotation of the crank lever 61 in the direction of Arrow A also causes the locking operation of the brake spring to be unlocked.
Even if one tries to raise or lower the window glass G without rotating the crank lever 61, the brake spring 92 performs the locking operation, since the diameter of the brake spring 92 increases, and the associating projection 97 of the drum 54a pushes the nail 92a or 92b of the brake spring 92.
As described above, as to the locking operation or the unlocking operation, it is necessary for one nail to move to some extent before the other nail moves for the purpose of increasing or decreasing the diameter of the brake spring. For the purpose, it is necessary to have some play between the associating projection 97 and the notch portion 95 in the rotational direction. If there is no play between them, both of the nails 92a, 92b are rotated at the same time, namely the diameter of the brake spring 92 cannot be increased or decreased. Accordingly, the locking operation and the unlocking operation do not operate.
Accordingly, the shaft 96 is rotatable in the range of the play against the housing 111 without rotating the drum 54 itself. In that case, the crank lever 61 fixed to the end 85 of the shaft 96 is shakable by an angle of about 30 degrees.
Thus, when the window regulator is installed in a car, or the like, there is a problem that the crank lever 61 shakes or makes a noise due to vibration of a car, or the like. The problem causes a driver to feel some displeasure.
Further, the shaking of the crank lever 61 causes the nails 92a, 92b of the brake spring 92 to repeatedly receive impulse force. There is another problem that the repeated impulse force causes the nails 92a, 92b to sustain a damage of fatigue. Therefore, the operation of the window regulator cannot be performed.
As a method for solving the above problems, it is thinkable to increase a frictional resistance of the shaft 96 and the housing 91 or a frictional resistance of the shaft 96 and the drum 54, but it is difficult to maintain the frictional resistance in a suitable range, and it is not useful to increase the frictional resistance because of making operational force to be heavy, and further, because of wearing out the sliding portion.
"Idling movement" or "move idly" described in the specification means that, when a torque due to the relative rotation of a first ratchet teeth and a second ratchet teeth by means of rotating a crank lever is generated, slant portions of the first ratchet teeth and the second ratchet teeth slip in the rotational direction with each other, and both ratchet teeth moves axially in the opposed direction with each other, at last the ratchet teeth engage again. Further, the conception of "idling movement" or "move idly" includes not only a case that one ratchet teeth moves in the axial direction and rotates around the axis, but also various cases, e.g. the case that one ratchet teeth moves in the axial direction and the other ratchet teeth rotates around the axis, or the case that both of the ratchet teeth move axially so as to depart away with each other, and one or both ratchet teeth rotate around the axis in the opposite directions.